Exogenous fibrolytic enzymes affect chemical compostition, animal intake and digestibility of guinea grass hay (Panicum maximum Jacq.)

Abstract

Two experiments were conducted for determining effects of applying exogenous fibrolytic enzymes to guineagrass hay (GH) [Panicum maximum Jacq. (= Urochloa maxima (Jacq.) R. Webster)] upon chemical composition, voluntary intake (VI), digestibility of various chemical fractions, and apparent and true dry matter (DM) degradability. The enzymatic products used were Promote^NET and Biocellulase^A-20, derived from Trichoderma longibratum and Aspergillus reesei. These products contain mainly cellulase and xylanase. In the first experiment, nine mature Blackbelly x creole crossbred rams of 26.8 kg mean body weight (BW) were used in a 3 x 3 Latin Square design, with 18-d periods. Treatments consisted of untreated hay (control), hay treated with Promote^NET, and hay treated with Biocellulase^A-20, applied by spraying 24 h prior to feeding. Daily hay offerings were at 4% of BW on a dry matter (DM) basis. Enzyme treatment increased contents of DM and crude protein (CP) in the treated GH in comparison with those contents of the untreated hay. A tendency to reduce neutral detergent fiber (NDF), acid detergent fiber (ADF) and hemicellulose concentrations through the enzymatic treatments was also observed but was not significant (P > 0.05). The VI of DM of hays treated with Biocellulase^A-20 and Promote^NET (1,139 and 938 g DM/d, respectively) exceeded that of the control (921 g DM/d).The VI of CP, NDF and ADF were higher for hay treated with Biocellulase^A-20  than for GH untreated or treated with Promote^NET. Rams fed enzyme-treated hay had higher (P < 0.05) DM intake as a percentage of BW when compared with those fed untreated GH (4.06% for Biocellulase^A-20 0, 3.15% for Promote^NET, and 2.86% for the control). Apparent DM digestibility increased (P < 0.05) by 5.89 and 4.24 percentage units for Biocellulase^A-20 - and Promote^NET -treated hays in comparison with that of the control (50.12%). Significant increases over the control were observed in digestibility of three other fractions for GH treated with Biocellulase^A-20 and Promote^NET (CP, 3.23 and 3.18; NDF, 7.96 and 4.31; ADF, 7.69 and 7.9 percentage units). Digestibility of dry matter, CP and ADF did not differ (P > 0.05) between enzymatic treatments, whereas NDF digestibility was higher (P < 0.05) for GH treated with Biocellulase^A-20. In the second experiment, apparent dry matter degradability (IVDMDA) and true dry matter degradability (IVDMDT) were found to be higher (P < 0.05) for GH treated with both enzymes than for those of the control (IVDMDA by 2.75 percentage units for Biocellulase^A-20, 2.12 for Promote^NET; IVDMDT by 2.42 and 1.73 units, respectively). These results indicate that application of fibrolytic enzymatic complexes to low-quality tropical grass hay can improve the nutritional value substantially.